[Demangle] Add support for D anonymous symbols

    Anonymous symbols are represented by 0 in the mangled symbol. We should skip
    them in order to represent the demangled name correctly, otherwise demangled
    names like `demangle..anon` can happen.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D114307

Author: ljmf00

llvm/lib/Demangle/DLangDemangle.cpp

@@ -200,6 +200,15 @@ const char *Demangler::parseQualified(OutputBuffer *Demangled,
   // Whether it has more than one symbol
   size_t NotFirst = false;
   do {
+    // Skip over anonymous symbols.
+    if (*Mangled == '0') {
+      do
+        ++Mangled;
+      while (*Mangled == '0');
+
+      continue;
+    }
+
     if (NotFirst)
       *Demangled << '.';
     NotFirst = true;

llvm/unittests/Demangle/DLangDemangleTest.cpp

@@ -34,4 +34,6 @@ INSTANTIATE_TEST_SUITE_P(
         std::make_pair("_D88", nullptr),
         std::make_pair("_D8demangleZ", "demangle"),
         std::make_pair("_D8demangle4testZ", "demangle.test"),
-        std::make_pair("_D8demangle4test5test2Z", "demangle.test.test2")));
+        std::make_pair("_D8demangle4test5test2Z", "demangle.test.test2"),
+        std::make_pair("_D8demangle4test0Z", "demangle.test"),
+        std::make_pair("_D8demangle4test03fooZ", "demangle.test.foo")));